With a coin like dash that uses a paynode scheme, all you need to do is keep reinvesting and you are guaranteed a greater percent of the stake
There are masternode costs involved, security and technical know-how costs (if you don't have the skills, you have to pay others to do it for you) as well as investment dilution by PoW mining.
The costs are negligible, as I think it was you who stated that a $5 VPS was more than sufficient. In fact you can probably run many masternodes on a $5 VPS with some knowhow.
This is not proof of stake where you have 1000 coins and they are giving you interest, 'just because'.
Actually it is. There is dilution, yes, but you would have dilution either way. The coins paid out in proportion to existing coin ownership is the
portion of coin supply that does not count as distribution, which is exactly what I said earlier.
If this is not clear, imagine a corporation with 1 million shares. There is a 2-for-1 stock split on Monday, "distributing" (but not really) 1 million new shares in proportion to existing ownership, followed by 1 million new shares being sold to an outside investor on Tuesday. The effect here is distribution aka dilution of not 2 million shares, but actually 500000 (of the original-pre-split shares).
This is relevant in comparing between emissions of different coins. Since Monero has no coins-for-coins PoS-ish scheme, the full amount of ongoing distribution dilutes earlier holdings (including "cripplemined" coins). In coins that do have these schemes, ongoing distribution is in effect greatly reduced.